sandbox/linux/seccomp-bpf/die.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "sandbox/linux/seccomp-bpf/die.h"
   6
   7 #include <errno.h>
   8 #include <signal.h>
   9 #include <stdio.h>
  10 #include <sys/prctl.h>
  11 #include <sys/syscall.h>
  12 #include <unistd.h>
  13
  14 #include <string>
  15
  16 #include "base/logging.h"
  17 #include "base/posix/eintr_wrapper.h"
  18 #include "sandbox/linux/seccomp-bpf/syscall.h"
  19 #include "sandbox/linux/services/syscall_wrappers.h"
  20 #include "sandbox/linux/system_headers/linux_signal.h"
  21
  22 namespace sandbox {
  23
  24 void Die::ExitGroup() {
  25   // exit_group() should exit our program. After all, it is defined as a
  26   // function that doesn't return. But things can theoretically go wrong.
  27   // Especially, since we are dealing with system call filters. Continuing
  28   // execution would be very bad in most cases where ExitGroup() gets called.
  29   // So, we'll try a few other strategies too.
  30   Syscall::Call(__NR_exit_group, 1);
  31
  32   // We have no idea what our run-time environment looks like. So, signal
  33   // handlers might or might not do the right thing. Try to reset settings
  34   // to a defined state; but we have not way to verify whether we actually
  35   // succeeded in doing so. Nonetheless, triggering a fatal signal could help
  36   // us terminate.
  37   struct sigaction sa = {};
  38   sa.sa_handler = LINUX_SIG_DFL;
  39   sa.sa_flags = LINUX_SA_RESTART;
  40   sys_sigaction(LINUX_SIGSEGV, &sa, nullptr);
  41   Syscall::Call(__NR_prctl, PR_SET_DUMPABLE, (void*)0, (void*)0, (void*)0);
  42   if (*(volatile char*)0) {
  43   }
  44
  45   // If there is no way for us to ask for the program to exit, the next
  46   // best thing we can do is to loop indefinitely. Maybe, somebody will notice
  47   // and file a bug...
  48   // We in fact retry the system call inside of our loop so that it will
  49   // stand out when somebody tries to diagnose the problem by using "strace".
  50   for (;;) {
  51     Syscall::Call(__NR_exit_group, 1);
  52   }
  53 }
  54
  55 void Die::SandboxDie(const char* msg, const char* file, int line) {
  56   if (simple_exit_) {
  57     LogToStderr(msg, file, line);
  58   } else {
  59     logging::LogMessage(file, line, logging::LOG_FATAL).stream() << msg;
  60   }
  61   ExitGroup();
  62 }
  63
  64 void Die::RawSandboxDie(const char* msg) {
  65   if (!msg)
  66     msg = "";
  67   RAW_LOG(FATAL, msg);
  68   ExitGroup();
  69 }
  70
  71 void Die::SandboxInfo(const char* msg, const char* file, int line) {
  72   if (!suppress_info_) {
  73     logging::LogMessage(file, line, logging::LOG_INFO).stream() << msg;
  74   }
  75 }
  76
  77 void Die::LogToStderr(const char* msg, const char* file, int line) {
  78   if (msg) {
  79     char buf[40];
  80     snprintf(buf, sizeof(buf), "%d", line);
  81     std::string s = std::string(file) + ":" + buf + ":" + msg + "\n";
  82
  83     // No need to loop. Short write()s are unlikely and if they happen we
  84     // probably prefer them over a loop that blocks.
  85     ignore_result(
  86         HANDLE_EINTR(Syscall::Call(__NR_write, 2, s.c_str(), s.length())));
  87   }
  88 }
  89
  90 bool Die::simple_exit_ = false;
  91 bool Die::suppress_info_ = false;
  92
  93 }  // namespace sandbox